Köttbullar are a Swedish institution. The key to their tender flavour is a mix of ground pork and beef, often softened with breadcrumbs soaked in cream or milk, and seasoned with nutmeg and allspice (or a touch of black pepper).
The sauce, made directly in the pan from the meatball drippings, is equally important. It should be creamy, rich, and salty. The combination with cold lingonberry jam is essential.
In a large bowl, mix the ground beef and pork. Add the sautéed onion and the breadcrumbs soaked in milk or cream. (Squeeze the breadcrumbs beforehand.)
Add the egg, salt, black pepper, nutmeg, and/or allspice. Mix everything thoroughly with your hands (not too long, to prevent the meat from becoming tough).
Shape small balls (approx. 2-3 cm diameter) with moistened hands.
Heat a mixture of butter and oil in a large pan. Fry the meatballs on all sides until golden brown and cooked through. Remove the meatballs and keep them warm, but leave the drippings in the pan.
Add butter to the pan with the drippings. Once melted, sprinkle in the all-purpose flour and sauté briefly. A dark roux will form.
Gradually pour in the broth, stirring constantly. Bring to a boil and stir until the sauce thickens. The sauce should be smooth.
Pour in the cream, soy sauce, and season with salt and white pepper. Let it gently bubble for 5 minutes.
Return the meatballs to the sauce and let them heat through for 2-3 minutes.
Serve hot with mashed potatoes, a large spoon of lingonberry jam, and pickled cucumbers.